Referring to FIG. 1 and the Cartesian coordinate system which comprises an x axis 102, a y axis 104, and a z axis 106 that are mutually orthogonal, a known air-cooling apparatus 100, described in U.S. Pat. No. 7,085,133, which is incorporated by reference herein in its entirety, includes a row of cabinets 108, including cabinets 110, 112, 114, 116 arrayed along the x axis 102. The row of cabinets 108 includes a first cabinet 110 located at the +x end of the row and a last cabinet 116 located at the −x end of the row. An arbitrary number of additional interior cabinets, such as cabinets 112 and 114 shown in FIG. 1, are positioned between the first cabinet 110 and the last cabinet 116.
An intake end-plenum 118, which includes a sloping wall 120, abuts the row of cabinets 108 at an upstream face 110a of the first cabinet 110 to direct cooled air thereto. An exhaust end-plenum 122, which includes a sloping wall 124, is adjacent to a downstream face 116b of the last cabinet 116 to direct exhaust air therefrom. Interposed between each pair of adjacent cabinets is a combined-plenum unit 126 that comprises both an intake plenum 128 and an exhaust plenum 130. Within each combined-plenum unit 126, the intake plenum 128 and the exhaust plenum 130 are separated from each other by a sloping wall 132. The combined plenum units 126 are mounted to the cabinets 110, 112, and 114 such that the exhaust plenums 130 thereof abut the cabinets' downstream surfaces 110b, 112b, and 114b respectively, and the intake plenums 128 thereof abut the cabinets' upstream surfaces 112a, 114a, and 116a, respectively. Each cabinet 110, 112, 114, 116 contains heat-producing electronics 134 arranged to allow airflow parallel to the x direction 102. Therefore, air-moving devices 136 in each cabinet are arranged to induce and encourage an S-shaped airflow 138. This type of cooling means is used, for example, in IBM®'s Bluegene®/L and Bluegene®/P supercomputers. The abutted row 108 of cabinets 110, 112, 114, 116 and plenums 118, 122, 126 stand in a room 140 on a raised floor 142 that is above and substantially parallel to a sub-floor 144. The raised floor 142 typically comprises a regular two-dimensional array of removable tiles 146 having pitch p in the x 102 and y 104 directions. Cooling air 148 is supplied to an under-floor space 150 between the raised floor 142 and the sub-floor 144 by a plurality of air-conditioning units 152 that are also known in the art.
Cooling one of the interior cabinets 112, 114 is accomplished by the S-shaped air-stream 138 passing through a hole 154 in the raised floor, and thereafter through the intake plenum 128. Drawn by the air-moving devices 136, the S-shaped air stream 138 travels over the heat-producing electronics 134, exiting the cabinet through the exhaust plenum 130. After the S-shaped air-stream 138 exits the exhaust plenum 130, it is returned to an open top surface 156 of the air conditioning units 152. Cooling of the first cabinet 110 or last cabinet 116 is similar to that for interior cabinets 114, except that the air enters the first cabinet 110 through the intake end plenum 118, and air exits the last cabinet 116 through the exhaust end plenum 122.
The known cooling apparatus 100 is deficient because it imposes at least the following several requirements on the room 140 and on the design of the cabinets 110, 112, 114, 116. First, each cabinet must be fed by an airflow rate V sufficient to keep all the cabinet's internal electronics 134 sufficiently cool. For cabinets that dissipate large quantities of heat, this requirement is often burdensome on the infrastructure of the room 140 because it requires significant investment in air-conditioning units 152, a large under-floor space 150, and a disruption of airflow patterns to other, already-existing equipment in the room.
Second, at the interface between any of the intake plenums 118, 128 and the abutting cabinets 110, 112, 114, 116 where the air-stream 138 first turns, the flow must be managed carefully, with appropriately designed turning aids, to avoid stagnation regions causing the electronics 134 to reach higher temperatures. This requirement is difficult to achieve in designing the cabinet, and despite best design efforts may be defeated by unusual raised-floor conditions, such as those where the distance between the raised floor 142 and the sub-floor 144 is too small, or where the hole 154 is partially obstructed by either structural members of the raised floor 142 or by equipment such as wires in under-floor space 150.
Third, in order to achieve high packing density of cabinets, the combined plenum unit 126 must be narrow. Thus, air must flow vertically through a relatively narrow intake plenum 128 and exhaust plenum 130. This requirement inevitably incurs pressure loss, leading to reduced flow rate V and increased temperature of the electronics 134.
Fourth, holes 154 must be cut in the raised floor 142 underneath each of the intake plenums 118 and 128. To avoid non-uniform flow leading to hotspots in the cabinet, the holes 154 must not be obstructed by structural members supporting the raised floor. Unobstructed holes are difficult to insure for all installations, because raised-floors are not standard worldwide, for example, the pitch p of the removable tiles 146 may differ from country to country.
Therefore, a need exists for an improved cooling apparatus and method of cooling a row of cabinets 108 that houses electronic equipment 134. It would be desirable, without sacrificing airflow through any particular item of the electronics 134, for the cooling apparatus to operate with the least possible total airflow, thereby minimizing both the cost of air-conditioning equipment 152 and the level of acoustical noise in the room 140. Further, it would be desirable to minimize constricted air passageways, such as the narrow plenums 128 and 130, that unduly limit airflow. Moreover, it would be desirable to avoid turns in the airflow path, such as those in the S-shaped airflow path 138, thereby to eliminate hotspots caused by flow non-uniformities and boundary-layer separation. Finally, it would be desirable to improve cabinet-packing density by minimizing the amount of space devoted exclusively to air handling, such as that occupied by plenums 118, 122, and 126.